Cationic polymers have been utilized widely as aids for paper making or agglomerating agents for treatment of water and especially as dehydrating aids for sewage sludge. The cationic polymer obtained from a monomer selected from the group consisting of a compound represented by Formula (I): ##STR1## a salt thereof and a derivative thereof quaternized with an alkylating agent; or the copolymer of said monomer with other water-soluble monomers such as acrylamide can give easily a polymer of high molecular weight, is suited for the above uses, thus being one of the typical cationic polymers industrially produced. Also, while the cationic polymer is used as an aqueous solution, it is generally traded in these days primarily as powder due to economy in transportation cost and easiness in handling (metering and dissolution).
As a process for producing a cationic vinyl polymer, an aqueous solution polymerization process is generally employed for the reason of its economy and easiness in obtaining a high molecular weight polymer. In this process, from the aspects of improvement of productivity and drying cost, the polymerization in higher monomer concentration has been investigated.
Typical examples of this process are disclosed in Japanese Laid-open patent Publication Nos. 80378/1975 and 133388/1976.
In these publications, polymerization is carried out in a highly concentrated aqueous solution with 80% or higher of a monomer comprising mainly the monomer of Formula [I] in a polymerization vessel, and the glassy solid obtained after cooling is crushed thereby to obtain efficiently a powdery cationic polymer. However, in practicing this process industrially, there is involved a serious problem in post-treatment of the polymer.
That is, when polymerization is carried out in a mass, the block produced will have a weight of at least 100 kg on an industrial scale, and it will take practically a whole 24 hours to cool this product to a crushable temperature. For this reason, a large space is required in production installation, and further the energy cost is greatly influenced by use of the cooling energy such as cold wind.
The present inventors have made investigations on the process for carrying out continuous polymerization on a movable carrier in order to further rationalize the aqueous solution polymerization of the monomer comprising mainly the monomer of Formula (I). In polymerization on a movable carrier, cooling can be performed more efficiently as compared with the polymer in shape of a mass, because a polymer shaped into a plate can be obtained. On the other hand, if the plate can be comminuted under a hot state, the time requiring cooling step can be substantially shortened to make the steps further simplified.
However, the plate-shaped polymer peeled off under a hot state from the movable carrier is a tough solid having slight softness, and it is almost impossible to crush it by an impact force and it cannot be thrown directly into a conventional crushing machine rotating at high speed on account of its shape.
Accordingly, the present inventors have investigated intensively on a process which can simplify the cooling step by comminuting the plate-shaped polymer under a hot state, and accomplished the present invention.